drivers: flash: nrf_qspi_nor: Fix no multithreading compilation

Fixing error introduced in 951e72b94769f55b0c2f2cf70f81d063ec81d11e
where ifdef was converted to IS_ENABLED. Ifdef was required because
element in the struct does not exist when multithreading is disabled.

Signed-off-by: Krzysztof Chruscinski <krzysztof.chruscinski@nordicsemi.no>
1 file changed